Tonight’s episode of CSI involved a rapist who was initially let go because his DNA sample from his epithelial cells didn’t match the DNA from the semen in the victim. They finally discover that he’s a chimera, and so his DNA is different in different tissues.
I realize that this is TV and they’re taking liberties with the truth, but I want to know just how off-base their explanation is.
They said that he was initially a fraternal twin, and “absorbed” his brother at a very early stage of development, and so now he has both sets of DNA, expressed in different tissues.
He didn’t know this till after his bone marrow donation was rejected by his leukemia-afflicted little brother. After the brother died, the doctors told this guy about his strange condition.
Absorbing a fraternal twin? Is that even possible, and would it create this type of man whose semen has one set of genes, and his skin cells another, and his blood cells both? I’ve heard of twin animals having blood exchange in utero, mixing their hematopoietic stem cells and leaving their blood with 2 separate sets of blood cells. But that shouldn’t affect the rest of the tissues.
Wouldn’t the tests for determining the bone marrow compatibility have picked up on the mosaicism? If both DNA sets are in the marrow (presumably the cause for the rejection), then both will be present in the blood cells… no?
I’m very very curious about all this now, so I hope someone out there knows about this stuff!